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Revision: 1.3
Committed: Sat Jul 9 04:11:30 2005 UTC (19 years, 4 months ago) by root
Branch: MAIN
Changes since 1.2: +7 -6 lines
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File Contents

# Content
1 NAME
2 Linux::AIO - linux-specific aio implemented using clone
3
4 SYNOPSIS
5 use Linux::AIO;
6
7 DESCRIPTION
8 This module implements asynchronous I/O using the means available to
9 Linux - clone. It does not hook into the POSIX aio_* functions because
10 Linux does not yet support these in the kernel (even as of 2.6.12, only
11 O_DIRECT files are supported) and even if, it would only allow aio_read
12 and write, not open, stat and so on.
13
14 Instead, in this module a number of (non-posix) threads are started that
15 execute your read/writes and signal their completion. You don't need
16 thread support in your libc or perl, and the threads created by this
17 module will not be visible to the pthreads library.
18
19 NOTICE: the threads created by this module will automatically be killed
20 when the thread calling min_parallel exits. Make sure you only ever call
21 min_parallel from the same thread that loaded this module.
22
23 Although the module will work with in the presence of other threads, it
24 is not reentrant, so use appropriate locking yourself.
25
26 Linux::AIO::min_parallel $nthreads
27 Set the minimum number of AIO threads to $nthreads. The default is
28 1, which means a single asynchronous operation can be done at one
29 time (the number of outstanding operations, however, is unlimited).
30
31 It is recommended to keep the number of threads low, as some linux
32 kernel versions will scale negatively with the number of threads
33 (higher parallelity => MUCH higher latency).
34
35 Linux::AIO::max_parallel $nthreads
36 Sets the maximum number of AIO threads to $nthreads. If more than
37 the specified number of threads are currently running, kill them.
38 This function blocks until the limit is reached.
39
40 This module automatically runs "max_parallel 0" at program end, to
41 ensure that all threads are killed and that there are no outstanding
42 requests.
43
44 $fileno = Linux::AIO::poll_fileno
45 Return the *request result pipe filehandle*. This filehandle must be
46 polled for reading by some mechanism outside this module (e.g. Event
47 or select, see below). If the pipe becomes readable you have to call
48 "poll_cb" to check the results.
49
50 Linux::AIO::poll_cb
51 Process all outstanding events on the result pipe. You have to call
52 this regularly. Returns the number of events processed. Returns
53 immediately when no events are outstanding.
54
55 You can use Event to multiplex, e.g.:
56
57 Event->io (fd => Linux::AIO::poll_fileno,
58 poll => 'r', async => 1,
59 cb => \&Linux::AIO::poll_cb );
60
61 Linux::AIO::poll_wait
62 Wait till the result filehandle becomes ready for reading (simply
63 does a select on the filehandle. This is useful if you want to
64 synchronously wait for some requests to finish).
65
66 Linux::AIO::nreqs
67 Returns the number of requests currently outstanding.
68
69 aio_open $pathname, $flags, $mode, $callback
70 Asynchronously open or create a file and call the callback with the
71 filedescriptor (NOT a perl filehandle, sorry for that, but watch
72 out, this might change in the future).
73
74 aio_close $fh, $callback
75 Asynchronously close a file and call the callback with the result
76 code.
77
78 aio_read $fh,$offset,$length, $data,$dataoffset,$callback
79 aio_write $fh,$offset,$length, $data,$dataoffset,$callback
80 Reads or writes "length" bytes from the specified "fh" and "offset"
81 into the scalar given by "data" and offset "dataoffset" and calls
82 the callback without the actual number of bytes read (or "undef" on
83 error).
84
85 aio_stat $fh_or_path, $callback
86 aio_lstat $fh, $callback
87 Works like perl's "stat" or "lstat" in void context. The callback
88 will be called after the stat and the results will be available
89 using "stat _" or "-s _" etc...
90
91 Currently, the stats are always 64-bit-stats, i.e. instead of
92 returning an error when stat'ing a large file, the results will be
93 silently truncated unless perl itself is compiled with large file
94 support.
95
96 aio_unlink $pathname, $callback
97 Asynchronously unlink a file.
98
99 BUGS
100 This module has been extensively tested in a large and very busy
101 webserver for many years now.
102
103 - aio_open gives a fd, but all other functions expect a perl filehandle.
104
105 SEE ALSO
106 Coro.
107
108 AUTHOR
109 Marc Lehmann <schmorp@schmorp.de>
110 http://home.schmorp.de/
111